G. Privalov et al., PRECISE SCANNING CALORIMETER FOR STUDYING THERMAL-PROPERTIES OF BIOLOGICAL MACROMOLECULES IN DILUTE-SOLUTION, Analytical biochemistry, 232(1), 1995, pp. 79-85
A precise scanning calorimeter for studying the heat capacity of liqui
ds in a broad temperature range has been developed. By its design and
capabilities this calorimeter is the first of a new generation for thi
s type of instrument. This new scanning calorimeter operates different
ially, is equipped with a pair of gold capillary cells and semiconduct
or sensors, and is able to scan up and down in temperature at user-sel
ected rates. This instrument is completely operated by an integrated c
omputer which also provides a full thermodynamic analysis of the resul
ts. Its construction does not involve the use of organic compounds, th
us eliminating a source of baseline noise that has affected previous c
alorimeters. The operational temperature range of the instrument can b
e varied between 0 and 120 degrees C. The gold capillary cells (operat
ional volume 0.8 ml) minimize temperature gradients in the heated/cool
ed liquid sample and permit easy washing and reloading without air bub
bles. These features are crucial for the accuracy of difference heat c
apacity measurements and determination of the absolute value of the pa
rtial heat capacity of solute molecules. The measurements can be perfo
rmed under an excess constant pressure (up to 3 atm) to prevent format
ion of gas bubbles and boiling of aqueous solutions above 100 degrees
C. The noise level of the recorded heating/cooling power difference is
below 50 x 10(-9) W (i.e., below 10 ncal/s) with a response half-time
of 5 s. The reproducibility of the baseline without refilling the cap
illary cells is on the order of 0.5 x 10(-6) W. Reproducibility of the
baseline upon refilling the cell is of the same order of magnitude. T
his provides an accuracy in difference heat capacity determination on
the order of 10 mu cal/degrees Kml at a heating rate of 1 degrees K/mi
n. (C) 1995 Academic Press, Inc.